Know the Fundamentals

“What is NFPA 72?” That sounds like a straightforward question, right? At least, we would like to think so. At a recent meeting, someone asked a technician this seemingly simple question. He replied correctly that NFPA 72 was the National Fire Alarm and Signaling Code. He then proceeded to add that the “72” was the year of the code. As if that response wasn’t jarring enough, he answered the question, “Does NFPA 72 tell you what you need to know about the installation of a fire alarm system?” with a surprising “No!”

Needless to say, I instantly knew that this technician’s company had failed to properly train him. He obviously had not read the code nor understood its role in fire alarm system application, design, installation, testing and maintenance.

How familiar are you with the code requirements contained in NFPA 72 2013? I know it is not as entertaining as a Stephen King or David Baldacci novel, but you have to read it to ensure you know what to do when designing and installing fire alarm systems.

Why is that so hard to understand? Maybe, as technicians become employed, they receive product information and on-the-job installation training with little introduction to, or instruction in the use of, the code. On the other hand, am I asking too much of a technician to know the basic requirements of the code? I don’t think so.

If you, as a technician or an owner, are uncomfortable reading this, maybe you need to pick up a copy of the latest edition of the code and actually read through it. Fire alarm system installation is certainly not rocket science, but the code contains specific rules we must follow to ensure the installed system provides the life safety protection we expect.

Many of the professional contractors I meet have a copy of the code, usually dog-eared, in their truck. Obviously, these professionals refer to it often, and therein lies the key: You do not have to memorize the code requirements. After all, it contains 351 pages of material. However, if you refer to it frequently, there is a good chance you will commit some of it to memory and install your systems in a code-compliant fashion.

Referencing the code during an installation, you will realize that you check out many of the same sections almost daily. For example, when you install smoke detectors in a corridor, the code permits the spacing to change. Do you know what that permitted change is?

First, the code provides the prescriptive spacing of smoke detectors in open areas, stating, “In the absence of specific performance-based design criteria, one of the following requirements shall apply:

1. “The distance between smoke detectors shall not exceed a nominal spacing of 30 ft (9.1 m) and there shall be detectors within a distance of one-half the nominal spacing, measured at right angles from all walls or partitions extending upward to within the top 15 percent of the ceiling height.

2. “All points on the ceiling shall have a detector within a distance equal to or less than 0.7 times the nominal 30 ft (9.1 m) spacing (0.7S).”

Annex section A.17.7.3.2.3.1 states, “The 30 ft (9.1 m) spacing is a guide for prescriptive designs. The use of such a spacing is based upon customary practice in the fire alarm community. Where there are explicit performance objectives for the response of the smoke detection system, the performance based design methods outlined in Annex B should be used. For the purposes of this section, ‘nominal 30 ft (9.1 m)’ should be determined to be 30 ft (9.1 m) ±5 percent [±18 in. (460 mm)].”

But, the answer to my corridor question is in item (2) above and described in Annex Section A.17.7.3.2.3.1(2): “This is useful in calculating locations in corridors or irregular areas… . For irregularly shaped areas, the spacing between detectors can be greater than the selected spacing, provided the maximum spacing from a detector to the farthest point of a sidewall or corner within its zone of protection is not greater than 0.7 times the selected spacing (0.7S).”

In plain English, this allows spacing of smoke detectors in a 10-foot-wide corridor with a smooth ceiling to be extended to 41 feet on center.

It should be obvious that knowledge of this one installation requirement and spacing options could make the difference in winning the bid for a job and making a profit. Get back to the basics, and read the code already!

Chapter 1 on fundamentals requires that alarm signals take priority over supervisory signals unless there is sufficient repetition of the alarm signal to prevent the loss of an alarm signal Chapter 1 on fundamentals requires that alarm signals take priority over supervisory signals unless there is sufficient repetition of the alarm signal to prevent the loss of an alarm signal Chapter 1 on fundamentals requires that alarm signals take priority over supervisory signals unless there is sufficient repetition of the alarm signal to prevent the loss of an alarm